RT1B/D+ non-lymphoid DC in early GVHD and Hg-induced autoimmunity of rat salivary and lacrimal glands

Experimental graft versus host disease in the (BN x LEW) F1 rat hybrid: an immunohistochemical study of early disease in oral mucosa

OBJECTIVE

To study the initial cellular events in oral mucosa (tongue) of experimental hyperplastic GVHD, in order to increase our understanding of the possible pathogenic mechanisms that may be shared with eg mercury (and other drug)-induced immunological reactions.

MATERIALS AND METHODS

GVHD was induced by one i.v. injection of 0.5-1 x 10(8) BN spleen cells into (BNxLEW)F1 hybrid rats. The pre-onset stages of the developing semiallogeneic GVHD were investigated in tongue mucosa by immunohistochemistry and monoclonal antibodies.

RESULTS

No detectable tissue infiltrates were found 24 h post induction. The pioneer cells appeared at day 3 and were RTIB+/CD2+ and RTIB1-/CD45 (240 kD)-/ EDI-/CD45RC-. At day 3, there was also a visible increase in spleen and lymph node size. Between day 3 and 7, there was a statistically significant increase of CD2+, RTIB+, TCR-alpha beta+, CD4+ and CD8+ cells, but no increase of NKR-PI+ cells. At day 10 there were focal accumulations of CD8+ and NKR-PI+ cells in subepithelial c.t. and in the basal parts of the adjacent epithelium. Animals not sacrificed earlier, showed signs of disease onset at day 11-14.

CONCLUSIONS

The early inflammatory infiltrate in this GVHD model consists of activated T cells of donor origin. We suggest, that these originally 'naive' cells migrate initially into lymphoid tissue and following an activation (day 3) enter host's peripheral tissue. Here, (allo-) antigen in constitutively RTIB1 (and EDI) expressing connective tissue dendritic cells may be immune targets of the primed T cells. Such interaction may lead to focal inflammation (increase of CD2+, RTIB+, TCR-alpha beta+, CD4+ and CD8+ cells) and to secondary epithelial damage executed by CD8+ and NKR-PI+ lymphocytes.

In vitro characterization of rat bone marrow-derived dendritic cells and their precursors

Although the rat is commonly used for basic immunology and transplantation research, phenotypic and functional characterization of rat dendritic cells (DCs) lags behind similar studies in the human and mouse. Therefore, these features were examined using DCs propagated from cultures of rat bone marrow maintained in a medium supplemented with granulocyte-monocyte colony-stimulating factor. Analysis of cytospin preparations of cultured cells showd that DCs arise from OX7+ myelomonocytic precursors. Typical mature rat DCs were morphologically similar to their mouse and human counterparts and expressed major histocompatibility complex (MHC) class II (common part determinant of Ia), OX62 (integrin molecule), OX7 (CD90), ICAM-1 (CD54), and CTLA4 counterreceptor, but were negative for OX8 (CD8), OX19 (CD5), W3/25 (CD4), and ED2, a rat macrophage marker. Functional analysis of OX62+ sorted DCs showed that they could effectively present the soluble antigen ovalbumin to naive T cells in vitro. A combination of anti-MHC class II monoclonal antibody and CTLA4-immunoglobulin inhibited allostimulatory ability more effectively than either reagent alone. Implications for studying the role of DCs in immune responses in the rat are discussed.

Experimental graft versus host disease in the (BN x LEW) F1 rat hybrid as a model for autoimmune disease. Study of early adenitis in lacrimal and salivary glands

We analysed inflammatory changes at selected time intervals, of salivary and lacrimal glands in the developing immunostimulatory [BN-->(BN x LEW)F1] model of graft-versus-host (GVH) reaction. A focal mononuclear adenitis in lacrimal and salivary glands developed at day 7 and increased clearly in "onset"-rats. Inflammatory responses in submandibular and parotid glands were less consistent and weaker than in lacrimal glands. There was no significant focus score difference between males and females. The lacrimal infiltrates were characterised immunohistochemically with monoclonal antibodies. Our findings indicate that CD4+ cells of donor origin dominated infiltrates, whereas a moderate number of B cells appeared only in large (late) foci. At stages corresponding to the onset of GVH disease (GVHD) in skin/labial mucosa, numerous CD8+ lymphocytes and NK cells were found in lacrimal glands, adjacent to ductal/ vascular plexa, sometimes forming small foci and with evidence of epithelial damage. We conclude that GVHD-associated T cell migration into rat exocrine glands occurs as a result of the semi-alloantigen-activated phenotype properties of the T cells. This activation occurs initially in lymphoid tissue and migration into glands is secondary to this and unrelated to antigen specificity. We also found evidence of amplification and tissue damage, interpreted as due to local reactivation of the T cells.